Trajectory guidance apparatus and method

Abstract

A trajectory guidance apparatus can guide motion with passive actuators with at least two degrees of freedom. The trajectory guidance apparatus has a linkage that is mounted to a reference and an interaction part that is to be manipulated by a master, such as a human, gravity g, water flow, a spring, or other force generator. The linkage has at least two force elements adapted to move the interaction part so that the interaction part is guided and can be moved along a prescribed path at a prescribed velocity relative to the reference. A controllable passive coupling connects the force elements and is adapted to impart passive forces against each force element of the linkage. The passive forces are derived substantially solely from a quantity of energy that is imparted to the interaction part by the master, not from other sources. A control mechanism controls the passive coupling, dynamically if desired, so that the interaction part is moved along a prescribed path of travel at a prescribed velocity by the force elements. The control mechanism essentially shifts energy from one force element to another force element during movement of the linkage so that the prescribed path and velocity are maintained.

Wherefore, the following is claimed: 
     
       1. A trajectory guidance apparatus capable of guiding motion with substantially passive elements with at least two degrees of freedom, comprising: a plurality of force elements, each of said force element corresponding to a degree of freedom;   an interaction part connected to said force elements, said interaction part adapted to move said force elements and to be guided by said force elements, when an external force is applied to said interaction part;   a controllable passive coupling connected to said force elements, said controllable passive coupling adapted to impart respective passive forces against said force elements to guide movement of said force elements, said passive forces being derived substantially from said external force that is imparted to said interaction part; and   a control means for controlling said controllable passive coupling so that said interaction part is guided along a prescribed path of travel by shifting energy from one of said force elements to another of said force elements.   
     
     
       2. The apparatus of claim 1, further comprising an interaction part position sensor adapted to sense a location of said interaction part, said interaction part position sensor configured to communicate a position signal to said control means, said control means configured to control said passive coupling along said prescribed path based upon said position signal. 
     
     
       3. The apparatus of claim 1, wherein said control means is adapted to control said controllable passive coupling so that said interaction part is guided along said prescribed path at a prescribed velocity by said force elements. 
     
     
       4. The apparatus of claim 1, wherein said control means dynamically controls said controllable passive coupling. 
     
     
       5. The apparatus of claim 1, wherein said passive coupling comprises a cylinder with an internal piston and a piston rod attached thereto associated with each said force element so that movement of said rod causes movement of said respective force element. 
     
     
       6. The apparatus of claim 1, wherein said passive coupling comprises a plurality of shafts, a differential mechanism interfacing at least two of said shafts, and a brake adapted to regulate rotation of one of said shafts. 
     
     
       7. The apparatus of claim 1, further comprising: a rectangular table frame having an inner rail;   mobile linear bearings adapted to ride along said rail;   a first force element of said force elements having one of said bearings disposed at its distal ends; and   a second force element of said force elements being prismatically mounted to said first force element and having one of said bearings at a distal end and one of said bearings near an end that supports said interaction part.   
     
     
       8. The apparatus of claim 1, further comprising: a parallelogram structure comprised of said force elements that are interconnected at pivotal joints, said interaction part being mounted to said parallelogram structure, said parallelogram structure adapted to rotate about a reference and adapted to radially move said interaction part relative to said reference;   a first cylinder connecting a pair of opposing joints of said parallelogram structure and adapted to provide said radial movement based upon extension and retraction of a first piston shaft associated with said first cylinder; and   a second cylinder connected between said parallelogram structure and said reference, said second cylinder adapted to provide said rotational movement based upon extension and retraction of a second piston shaft associated with said second cylinder.   
     
     
       9. The apparatus of claim 1, further comprising: a parallelogram structure comprised of said force elements that are interconnected at pivotal joints, said interaction part being mounted to said parallelogram structure, said parallelogram structure adapted to rotate about a reference and adapted to radially move said interaction part relative to said reference;   a rotatable inner shaft;   rotatable first and second outer shafts;   a differential mechanism interfacing said first and second outer shafts;   a first brake adapted to couple said first force element to said inner shaft;   a second brake adapted to couple said first force element to a reference;   a third brake adapted to couple said second force element to said second outer shaft; and   a fourth brake adapted to couple said second force element to a reference.   
     
     
       10. The apparatus of claim 1, (a) wherein said coupling comprises (i) rotatable first and second shafts, (ii) first and second brakes adapted to regulate rotation of said first and second shafts respectively; and (iii) a clutch interfacing said shafts; (b) wherein said force elements are first and second cables wound about said first and second shafts respectively; and (c) wherein said interaction part is connected to said cables. 
     
     
       11. The apparatus of claim 5, wherein each said cylinder is connected to another to permit exchange of fluid therebetween. 
     
     
       12. The apparatus of claim 7, wherein said passive coupling comprises a plurality of shafts, a differential mechanism interfacing at least two of said shafts, a brake adapted to regulate rotation of one of said shafts, and pulleys driven by said shafts and connected via belts to said bearings. 
     
     
       13. The apparatus of claim 7, wherein said passive coupling comprises a cylinder with an internal piston and a piston rod attached thereto associated with each said force element so that movement of said rod causes movement of said respective force element. 
     
     
       14. A trajectory guidance method for guiding motion with substantially passive elements with at least two degrees of freedom, comprising the steps of: applying an external force to an interaction part of a linkage having at least two force elements and two degrees of freedom in order to move said interaction part;   forcing said force elements to move, as said interaction part moves, via energy derived substantially from an external force and via coupling of passive forces applied by said force elements; and   guiding movement of said interaction part along a prescribed path via said force elements by controlling said passive forces imparted upon said interconnected force elements, by shifting energy from one of said force elements to another of said force elements.   
     
     
       15. The method of claim 14, further comprising the steps of: sensing a location of said interaction part; and   guiding said movement based upon said sensed location.   
     
     
       16. The method of claim 14, further comprising the step of guiding said interaction part along said prescribed path at a prescribed velocity with said force elements. 
     
     
       17. The method of claim 14, further comprising the step of utilizing a differential with first and second shafts to couple said passive elements, said first and second shafts being engaged with first and second force elements respectively that are connected to said interaction part. 
     
     
       18. The method of claim 14, further comprising the step of exchanging fluid between fluid cylinders associated with each of said force elements in order to couple said passive elements, each of said cylinders having an internal piston and a piston rod attached thereto associated with each said force element so that movement of said rod causes movement of said respective force element. 
     
     
       19. The method of claim 14, wherein said linkage comprises a parallelogram structure comprised of said force elements that are interconnected at pivotal joints, said interaction part being mounted to said parallelogram structure, said parallelogram structure adapted to rotate about a reference and adapted to radially move said interaction part relative to said reference. 
     
     
       20. A trajectory guidance method for guiding motion with passive elements with at least two degrees of freedom, comprising the steps of: applying an external force to an interaction part of a linkage having at least two force elements and two degrees of freedom in order to move said interaction part;   forcing said force elements to move via energy derived solely from said external force and coupling of passive forces applied by said force elements to each other;   guiding movement of said interaction part along a prescribed path via said force elements by controlling said passive forces imparted upon said interconnected force elements; and   utilizing a differential and a plurality of shafts to couple said passive elements, said plurality of shafts being engaged with said at least two force elements that are connected to said interaction part.